Untitled

<!doctype html>
<html>
<head>
<script type="text/javascript">
function changecolour()
{
  document.getElementById("box").style.background = document.getElementById("colour").value;
}
</script>
</head>

<body>
<div id="box" style="width:100px; height:100px; border:1px solid #000;"></div><br />
<input type="text" value="#aa0000" id="colour" /><input type="button" value="Click it!" onclick="changecolour();" />
</body>
</html>